Electrochromism refers to a perceptible and reversible change displayed by materials when an electrical charge is applied that causes an electrochemical redox reaction in materials said to be “electrochromic”. Transition metal oxides are one family of materials known to possess electrochromic properties. Electrochromic materials can be used to control the amount of light and heat allowed to pass through transparent media, such as, for example, rear-view mirrors that are tinted in response to various lighting conditions. Further examples of electrochromic materials and devices include electrochromic windows that have found utility in airliner windows where light passage through the windows is impeded when the device is in a charged state.
Electrochromic devices (“ECDs”) can reversibly control optical properties such as optical transmission, absorption, reflectance, and emittance, etc., through the application of an electric voltage. Such ECDs include devices such as “smart glass” or “switchable glass”, mirrors and display devices. Such ECDs typically comprise an electrochromic layer “sandwiched” between by an electrolytic layer.
Electrochromic windows, also known as “smart windows” have been installed in buildings and vehicles to achieve desired energy efficiency and indoor comfort levels by varying the transmittance of light and solar energy.
Electrochromic arrays comprise layers of material that can be deposited onto a transparent substrate for the purpose of changing the appearance and function of the substrate itself. Thin films of conductive material are disposed onto substrates, and influence adjacently positioned electrochromic materials that are responsive to an applied electric field, with the electrochromic material changing properties from a high-transmittance, non-light absorbing state to a lower-transmittance state capable of absorbing or reflecting incident light. When the electric field is discontinued, or electric polarity is reversed, the electrochromic material in an electrochromic material layer then reverts to its original state and assumes its original transmissive and non-light absorbing properties.
Electrochromic arrays can have distinct layers deposited onto a substrate, and a collection of thin film layers collectively referred to as an electrochromic “stack”. Such a layered electrochromic “stack” can include: a first conductive layer, an electrochromic layer, an ion conducting later, a counter electrode and a second conductive layer.